1. Field of the Invention
The present invention relates to an organic EL panel including plural pixels each having an organic EL element, and more particularly to an organic EL panel having, in each pixel, a micro-resonator (i.e., microcavity) capable of enhancing the light of a specific wavelength.
2. Description of the Related Art
A flat panel display (FPD) is a prospective display device having a thin and compact structure. Some liquid crystal displays, which are a type of FPD, are practically used in various devices. Furthermore, there are light emitting devices (e.g., display devices or light sources) including self-luminous type electro-luminescence elements (hereinafter, referred to as “EL elements”). In particular, organic EL display devices (i.e., organic EL panels) can produce a variety of luminescent colors depending on organic compound materials contained in the organic EL elements.
The organic EL display devices are the self-luminous type and accordingly different from liquid crystal displays or other display devices that control the transmissivity of the light emitted from a back light. Thus, the organic EL display devices have excellent efficiency in the use of light. Namely, the organic EL display devices can realize highly effective and bright emission of the light.
However, the organic EL element includes an organic layer that tends to deteriorate depending on conditions of use. In particular, to increase the brightness of the light, the injection current to the organic layer can be increased. In such a case, the organic layer deteriorates significantly.
As discussed in Japanese Patent Application Laid-open NO. hei06-275381, or in “Element Employing an Optical Resonator Structure” by Takahiro NAKAYAMA and Atsushi SUMIDA, the Japan Society of Applied physics, Molecular Electronics and Bioelectronics division, 1993, third meeting, p 135-p 143, it is known that an EL display device employing a micro-resonator (i.e., microcavity) can enhance the light of a specific wavelength.
However, the viewing angle dependence of a display color is not negligible when the microcavity is used, because an optical length of the microcavity when seen from the vertical direction is different from an optical length seen from an oblique direction. Accordingly, the wavelength of the enhanced light varies depending on the viewing angle.
It is therefore necessary to reduce or eliminate the viewing angle dependence caused by the microcavity.